Margot Kidder, the actress who played Lois Lane in the 1978 'Superman' movie, has died at the age of 69, the Guardian reported.

She was discovered in her Montana home over the weekend where she was unresponsive. Police pronounced the actress dead at the scene. [VIDEO]

While the police do not suspect any foul play was involved in her death, a full investigation is being conducted to learn what happened. No further details are known at this time.

Margot Kidder's rise to fame

Kidder gained a great deal of recognition for her early work, which included starring opposite Gene Wilder in the 1970 film "Quackser Fortune Has a Cousin in the Bronx," but it was her casting in superhero flick "Superman" along with Christopher Reeve that really sparked her career.

The titular character is still going strong to this day. [VIDEO]

She then reprised her role as the smart-mouthed journalist in all three of the franchise's sequels throughout the 1980s. Kidder also appeared in horror classics "The Amityville Horror" and "Black Christmas."

She continued to act up to the year 2018, staring in multiple Movies and several television shows along the way. Two of her projects are still in post-production.

Other projects under her belt included television shows "McQueen" and "The Mod Squad," and Kidder paired with several big names including James Garner and Robert Redford.

Outside of acting

Canadian-born Kidder became an American citizen in 2005, and outside of her acting career, was a political and women's rights activist.

She was an outspoken critic of the Gulf War, opposed fracking plans by energy companies, and was a vocal supporter of the Democratic political party.

Kidder's women's rights activism started when she settled in Montana and became a supporter of 'Montana Women For.' She was also arrested in 2011 for her involvement in a protest at the White House against the Keystone XL pipeline construction.

Kidder also suffered from mental health problems throughout her life and career, though she was very open about her struggles with Bipolar Disorder.

While working on her autobiography, a computer virus erased her work so far - she told People magazine in 1996 - which she believed was deliberate and caused by her former husband and the CIA. This caused Kidder to disappear for several days.

After she was found safe, Kidder would begin to talk openly about her experiences with depression and manic episodes, as well as striving to raise awareness of Bipolar Disorder and alternative treatments.

Margot Kidder was married and divorced three times, and is survived by her only child, Maggie, and her two grandchildren.